(a) Field of the Invention
The present invention relates to an electrolyte for a rechargeable lithium battery and a rechargeable lithium battery including the same. More preferably, the present invention relates to an electrolyte for a rechargeable lithium battery that shows excellent output characteristics due to a resistance reduction at a low temperature and a rechargeable lithium battery including the same.
(b) Description of the Related Art
In recent times, due to reductions in size and weight of portable electronic equipment, there has been a need to develop batteries for use in the portable electronic equipment, where the batteries have both high performance and large capacity. Furthermore, it is required that such batteries be produced in a cost effective manner and have improved safety.
Batteries are generally classified as primary batteries, which can be used only once and are then disposed of, and rechargeable batteries, which can be recharged and used repeatedly. Primary batteries include manganese batteries, alkaline batteries, mercury batteries, and silver oxide batteries. Rechargeable batteries include lead-acid storage batteries, nickel-metal hydride (Ni-MH) batteries, sealed nickel-cadmium batteries, lithium metal batteries, lithium ion batteries, lithium polymer batteries, and lithium-sulfur batteries.
Such batteries generate electric power using an electrochemical reaction material (referred to hereinafter simply as the “active material”) for a positive electrode and a negative electrode. Important factors for determining battery performance, such as capacity, cycle-life, power, safety, and reliability, include the electrochemical characteristics and the thermal stability of the active material used. Thus, extensive research has been undertaken to improve these factors of positive and negative active materials.
Of the currently available active materials for the negative electrode of the battery, lithium metal has a high electrical capacity per unit mass and high electro-negativity. Thus, lithium metal can be well adapted for use in producing high capacity and high voltage battery cells. However, since it is difficult to assure the safety of a battery using the lithium metal, other materials that can reversibly deintercalate and intercalate lithium ions are being used extensively for the active material of the negative electrodes in rechargeable lithium batteries.
Lithium rechargeable batteries generate electrical energy from changes of chemical potential during the intercalation/deintercalation of lithium ions at the positive and negative electrodes. Lithium rechargeable batteries use materials that reversibly intercalate or deintercalate lithium ions during charge and discharge reactions for both positive and negative active materials, and contain an organic electrolyte or a polymer electrolyte between the positive electrode and the negative electrode.
The electrolyte includes, for example, a cyclic carbonate having a high dielectric constant such as propylene carbonate, ethylene propylene carbonate, and so on, or a linear carbonate having low viscosity such as diethyl propylene carbonate, methylethyl propylene carbonate, dimethyl carbonate, and so on, and mixed solvents thereof.
Such an electrolyte may be decomposed on a surface of an electrically active electrode, and the internal resistance of a battery may be increased by the electrolyte decomposition. Accordingly, charge and discharge characteristics of a battery may be deteriorated and cycle-life is shortened. There has been a need for an electrolyte having excellent cell loading characteristics, low temperature characteristics, charge and discharge cycle characteristics, storage characteristics at high temperature, and so on.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.